There are lots of things that people are unwilling to think about. Given that that's the case (for whatever reason), maybe a psychological mechanism that separated out those things and enabled people to think about them in an emotionally uncommitted way would be of benefit. But thinking hypothetically about that sort of mechanism raises the problem that the worse things are the more upsetting they are to think about, and even if people had a mechanism that made them less committed to the things in question that might still be a problem, especially (this is the clever bit) when they were trying to gauge just HOW bad the bad things are. How to solve this problem? Have a psychological mechanism that separates out bad things, incorporates a gauge of how bad they are, but REVERSES the polarity, so that the worse things are the more fun they are to think about in this special sandbox. That's humour.

Application to the Spanish Inquisition is obvious, right?

And in general, this explains why people like us like anal jokes about people getting intellectual things wrong. Because there's nothing scarier for us than the thought that people are idiots.

Every time I try to apply this theory I find I can make it work, but I have to say a lot of ad hoc things about the details, so I think it's extremely incomplete.

I haven't seen this theory anywhere else, even as a small part of any other theory. Even if it's embarrassingly incomplete, and even if it's no use for the comparison with theorems, I think it's worth having.